1. Field of the Invention
The present invention relates to waveform-level detectors and to circuits therefor. Such detectors are particularly suited for use in conjunction with applied waveforms having positive and negative excursions relative to a neutral axis.
2. Description of the Prior Art
Such waveforms are frequently produced, for example, in apparatus associated with the recording of digital data and in particular in apparatus for reading data previously magnetically recorded on a magnetic medium by means of a transducer head. Such apparatus may record digital information by flux reversals in the medium which produce positive and negative signals upon being read out. It is customary to differentiate the signals produced by the transducing head and the resultant waveform exhibits the positive and negative excursions about the neutral axis referred to above, a flux reversal in the magnetic medium being represented in the waveform as a point at which the waveform trace crosses the axis. Hence, such crossover points are indicative of significant digital representations in the magnetic record.
However, in addition to these significant crossovers, other crossovers are frequently detected in an output waveform, being produced by noise in the detection circuits, for example, or simply by minute particles of dirt on the medium. The tendency to produce spurious outputs is increased as, for example, the packing density of digital recording on the medium decreases, the resultant waveform then exhibiting characteristic shoulders at which points noise is the more likely to produce spurious crossovers.